| 1. |
- Singh, Bhupender L., et al.
(författare)
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Cefuroxime axetil loaded solid lipid nanoparticles for enhanced activity against S. aureus biofilm
- 2014
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Ingår i: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 121, s. 92-98
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Tidskriftsartikel (refereegranskat)abstract
- The present research work is focused on the development of solid lipid nanoparticles of cefuroxime axetil (CA-SLN) for its enhanced inhibitory activity against Staphylococcus aureus produced biofilm. CA-SLN was prepared by solvent emulsification/evaporation method using single lipid (stearic acid (SA)) and binary lipids (SA and tristearin (TS)). Process variables such as volume of dispersion medium, concentration of surfactant, homogenization speed and time were optimized. The prepared SLN were characterized for encapsulation efficiency, drug polymer interaction studies (DSC and FT-IR), shape and surface morphology (SEM and AFM), in vitro drug release, stability studies and in vitro anti biofilm activity against S. aureus biofilm. Among the process variables, increased volume of dispersion medium, homogenization speed and time led to increase in particle size whereas increase in surfactant concentration decreased the particle size. SLN prepared using binary lipids exhibited higher entrapment efficiency than the single lipid. DSC and FT-IR studies showed no incompatible interaction between drug and excipients. CA-SLN showed two folds higher anti-biofilm activity in vitro than pristine CA against S. aureus biofilm.
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| 2. |
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| 3. |
- Chai, Qian, et al.
(författare)
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Organization of Ribosomes and Nucleoids in Escherichia coli Cells during Growth and in Quiescence
- 2014
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 289:16, s. 11342-11352
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Tidskriftsartikel (refereegranskat)abstract
- Background: We studied ribosome and nucleoid distribution in Escherichia coli under growth and quiescence. Results: Spatially segregated ribosomes and nucleoids show drastically altered distribution in stationary phase or when treated with drugs affecting translation, transcription, nucleoid-topology, or cytoskeleton. Ribosome inheritance in daughter cells is frequently unequal. Conclusion: Cellular growth processes modulate ribosome and nucleoid distribution. Significance: This provides insight into subcellular organization of molecular machines. We have examined the distribution of ribosomes and nucleoids in live Escherichia coli cells under conditions of growth, division, and in quiescence. In exponentially growing cells translating ribosomes are interspersed among and around the nucleoid lobes, appearing as alternative bands under a fluorescence microscope. In contrast, inactive ribosomes either in stationary phase or after treatment with translation inhibitors such as chloramphenicol, tetracycline, and streptomycin gather predominantly at the cell poles and boundaries with concomitant compaction of the nucleoid. However, under all conditions, spatial segregation of the ribosomes and the nucleoids is well maintained. In dividing cells, ribosomes accumulate on both sides of the FtsZ ring at the mid cell. However, the distribution of the ribosomes among the new daughter cells is often unequal. Both the shape of the nucleoid and the pattern of ribosome distribution are also modified when the cells are exposed to rifampicin (transcription inhibitor), nalidixic acid (gyrase inhibitor), or A22 (MreB-cytoskeleton disruptor). Thus we conclude that the intracellular organization of the ribosomes and the nucleoids in bacteria are dynamic and critically dependent on cellular growth processes (replication, transcription, and translation) as well as on the integrity of the MreB cytoskeleton.
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| 4. |
- Dongre, Mitesh, et al.
(författare)
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Flagella-mediated secretion of a novel Vibrio cholerae cytotoxin affecting both vertebrate and invertebrate hosts
- 2018
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Ingår i: Communications Biology. - : Springer Nature Publishing AG. - 2399-3642. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Using Caenorhabditis elegans as an infection host model for Vibrio cholerae predator interactions, we discovered a bacterial cytotoxin, MakA, whose function as a virulence factor relies on secretion via the flagellum channel in a proton motive force-dependent manner. The MakA protein is expressed from the polycistronic makDCBA (motility-associated killing factor) operon. Bacteria expressing makDCBA induced dramatic changes in intestinal morphology leading to a defecation defect, starvation and death in C. elegans. The Mak proteins also promoted V. cholerae colonization of the zebrafish gut causing lethal infection. A structural model of purified MakA at 1.9 Å resolution indicated similarities to members of a superfamily of bacterial toxins with unknown biological roles. Our findings reveal an unrecognized role for V. cholerae flagella in cytotoxin export that may contribute both to environmental spread of the bacteria by promoting survival and proliferation in encounters with predators, and to pathophysiological effects during infections.
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| 5. |
- Ghosh, Jaydip, et al.
(författare)
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Sporulation in mycobacteria
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 106:26, s. 10781-10786
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Ghosh, Jaydip, et al.
(författare)
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Sporulation in mycobacteria
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:26, s. 10781-10786
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Tidskriftsartikel (refereegranskat)abstract
- Mycobacteria owe their success as pathogens to their ability to persist for long periods within host cells in asymptomatic, latent forms before they opportunistically switch to the virulent state. The molecular mechanisms underlying the transition into dormancy and emergence from it are not clear. Here we show that old cultures of Mycobacterium marinum contained spores that, upon exposure to fresh medium, germinated into vegetative cells and reappeared again in stationary phase via endospore formation. They showed many of the usual characteristics of well-known endospores. Homologues of well-known sporulation genes of Bacillus subtilis and Streptomyces coelicolor were detected in mycobacteria genomes, some of which were verified to be transcribed during appropriate life-cycle stages. We also provide data indicating that it is likely that old Mycobacterium bovis bacillus Calmette-Guérin cultures form spores. Together, our data show sporulation as a lifestyle adapted by mycobacteria under stress and tempt us to suggest this as a possible mechanism for dormancy and/or persistent infection. If so, this might lead to new prophylactic strategies.
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| 7. |
- Joshi, Bishnu, et al.
(författare)
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Transcriptome Profiling of Staphylococcus aureus Associated Extracellular Vesicles Reveals Presence of Small RNA-Cargo
- 2021
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Ingår i: Frontiers in Molecular Biosciences. - : Frontiers Media S.A.. - 2296-889X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial extracellular vesicles (EVs) have a vital role in bacterial pathogenesis. However, to date, the small RNA-cargo of EVs released by the opportunistic pathogen Staphylococcus aureus has not been characterized. Here, we shed light on the association of small RNAs with EVs secreted by S. aureus MSSA476 cultured in iron-depleted bacteriologic media supplemented with a subinhibitory dosage of vancomycin to mimic infection condition. Confocal microscopy analysis on intact RNase-treated EVs indicated that RNA is associated with EV particles. Transcriptomic followed by bioinformatics analysis of EV-associated RNA revealed the presence of potential gene regulatory small RNAs and high levels of tRNAs. Among the EV-associated enriched small RNAs were SsrA, RsaC and RNAIII. Our finding invites new insights into the potential role of EV-associated RNA as a modulator of host-pathogen interaction.
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| 8. |
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| 9. |
- Mortezaei, Narges, et al.
(författare)
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Antibodies Change the Mechanics of Adhesion Fimbriae : a Case Study of CS20 Fimbriae Expressed by Enterotoxigenic Escherichia Coli
- 2015
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Ingår i: Biophysical Journal. - : Cell Press. - 0006-3495 .- 1542-0086. ; 108, s. 602-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Enterotoxigenic Escherichia coli (ETEC) express a variety of fimbriae that mediate adhesion to host epithelial cells. It has been shown that the ability of a fimbriated bacterial cell to attach and stay attached to host cells does not merely depend on the adhesin expressed distal of the fimbriae but also the biomechanical properties of the fimbriae are vital for sustained adhesion. Fimbriae can significantly extend under a constant force when exposed to an external force and therefore reduce the load on the adhesin, which is believed to help bacteria to withstand external forces applied by various body defense systems. Thus, it is thought that the fimbrial shaft and adhesin have co-evolved for optimal function when bacteria attach to host cells. To investigate if antibodies, normally found in the intestines, affects the biomechanical properties of fimbriae, we exposed CS20 fimbriae expressed by ETEC to anti-fimbrial antibodies and measured these properties using optical tweezers force spectroscopy. Our data show a change in the force required to extend the fimbriae and that the elasticity is significantly reduced by the presence of antibodies. The reduced elasticity, likely due to cross-linking of fimbrial subunits, could thus be another assignment for antibodies; in addition to their mission in marking bacteria as foreign, our data indicate that antibodies physically compromise fimbrial function. To further confirm interaction of antibodies to their specific target we performed western blot analysis, transmission electron microscopy and immunofluoresence microscopy. In the presence of antibodies, we suggest that our assay and results will be a starting point for further studies aimed at inhibiting bacterial adhesion by antibodies.
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| 10. |
- Mortezaei, Narges, 1985-, et al.
(författare)
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Biomechanical and Structural features of CS2 fimbriae of Enterotoxigenic Escherichia coli
- 2015
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Ingår i: Biophysical Journal. - : Elsevier. - 0006-3495 .- 1542-0086. ; 109:1, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea worldwide, and infection of children in underdeveloped countries often leads to high mortality rates. Isolated ETEC express a plethora of colonization factors (fimbriae/pili), of which CFA/I and CFA/II that are assembled via the alternate chaperone pathway (ACP), are amongst the most common. Fimbriae are filamentous structures, whose shafts are primarily composed of helically arranged single pilin-protein subunits, with a unique biomechanical capability allowing them to unwind and rewind. A sustained ETEC infection, under adverse conditions of dynamic shear forces, is primarily attributed to this biomechanical feature of ETEC fimbriae. Recent understandings about the role of fimbriae as virulence factors are pointing to an evolutionary adaptation of their structural and biomechanical features. In this work, we investigated the biophysical properties of CS2 fimbriae from the CFA/II group. Homology modelling its major structural subunit CotA reveals structural clues and these are related to the niche in which they are expressed. Using optical tweezers force spectroscopy we found that CS2 fimbriae unwind at a constant force of 10 pN and have a corner velocity of 1300 nm/s, i.e., the velocity at which the force required for unwinding rises exponentially with increased speed. The biophysical properties of CS2 fimbriae assessed in this work classify them into a low-force unwinding group of fimbriae together with the CFA/I and CS20 fimbriae expressed by ETEC strains. The three fimbriae are expressed by ETEC, colonize in similar gut environments, and exhibit similar biophysical features, but differ in their biogenesis. Our observation suggests that the environment has a strong impact on the biophysical characteristics of fimbriae expressed by ETEC.
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